Apparatus for splicing wires

ABSTRACT

An apparatus is provided for splicing wires, which apparatus includes shaping means for shaping a blank strip material into an approximate U-shape, and die means including a bottom wall and two side walls. The walls define a die cavity having an open side spacedly opposite the bottom wall between the side walls. The bottom wall has an elongated ridge spacedly intermediate the side walls and two concavely arcuate face portions whose axes of curvature are parallel to the ridge and which connect the same to the side walls. The apparatus also includes a ram member, moving means for moving the ram member inward of the cavity through the open side toward the bottom wall, and means for placing the shaped blank in the path of movement of the ram member for insertion of the blank into the cavity by the ram member and crimping of the blank by sliding contact with the side walls. The cavity is open longitudinally of the ridge for insertion of wires to be spliced. The ram member has a front face opposite the bottom wall, which front face has a crest and flares from the crest in a direction away from the bottom wall. The crest of the front face is transverse to the ridge of the bottom wall.

United States Patent [191 Garfinkel [4 1 Jan. 8, 1974 APPARATUS FOR SPLICING WIRES Jack Garfinkel, Bayside, NY. [73] Assignee: Genstape, Inc.

[22] Filed: June 1, 1972 [2]] Appl. No.: 258,809

Related U.S. Application Data [62] Division of Ser. No. 21,363, March 20, 1970, Pat.

[75] Inventor:

[52] U.S. Cl 29/203 D [5l]- Int. Cl H01! 43/04 [58] Field of Search ..l 29/203 D, 628, 203 R [56] References Cited UNITED STATES PATENTS 2,002,220 5/l935 Douglas 29/203 D 2,480,280 8/1949 Bergan 339/276 T 3,636,6ll l/l972 Rosenbaum 29/203 D Primary Examiner-Thomas H. Eager [57] ABSTRACT An apparatus is provided for splicing wires, which apparatus includes shaping means for shaping a blank strip material into an approximate U-shape, and die means including a bottom wall and two side walls. The walls define a die cavity having an open side spacedly opposite the bottom wall between the side walls. The bottom wall has an elongated ridge spacedly intermediate the side walls and two concavely arcuate face portions whose axes of curvature are parallel to the ridge and which connect the same to the side walls.

The apparatus also includes a ram member, moving means for moving the ram member inward of the cavity through the open side toward the bottom wall, and means for placing the shaped blank in the path of movement of the ram member for insertion of the blank into the cavity by the ram member and crimping of the blank by sliding contact with the side walls. The cavity is open longitudinally of the ridge for insertion of wires to be spliced.

' The ram member has a front face opposite the bottom wall, which front face has a crest and flares from the crest in a direction away from the bottom wall. The crest of the front face is transverse to the ridge of the bottom wall.

5 Claims, 11 Drawing Figures PATENTEDJAH 8|974 3,783,490

' sum 10E 3 PATENTED JAN 8 I974 SBEEI 2 OF 3 PATENIEDJAM 8%974 3383,1490

SHiEI 30? 3 1 APPARATUS FOR SPLICING WIRES 'This is a division, of application Ser. No. 21 ,363 filed Mar. 20, 1970 US. Pat. No. 3,685,148.

This invention relates to wire splices, and particularly to a splice made-by crimping a conductive connector member about sections of the wires to be connected, and to apparatus for making the splice. In its more specific aspects the invention is concerned with the making of conductive splices between insulated wires without prior removal of the insulating material in a separate step.

In an earlier, commonly owned application, Ser. No. 810,759, filed on Mar. 26, 1969, now US. Pat. No. 3,636,611, there was disclosed and claimed apparatus for splicing wires by means of connectors made by the apparatus from a continuous length of metal strip or flat wire and crimped about wires inserted in a die.

While the earlier apparatus is often effective in making conductive splices of magnet wires carrying an insulating layer of phenolic or similar brittle varnish composition, the splices made are of relatively high electrical resistance, and the effective contact area between the wires and the connector is usually quite small. The more recently adapted, relatively ductile varnishes are not readily broken on the machine of the earlier application.

An object of the invention is the provision of a splice which connects magnet wires without offering substantial resistance to the passage of electric current, and of apparatus for making the splice.

With this object and others in view, as will hereinafter become apparent, the splice of the invention essentially consists of two elongated wires of conductive metal, a continuous coating of insulating material on respective first sections of the wires, and a connector member of conductive strip material conformingly crimped about respective second sections of the wires. The first sections are of practically. uniform, normally circular cross section, and the second sections are juxtaposed and have respective longitudinally coextensive parts of a cross section which is elongated transversely of the direction of wire elongation, the cross sectional area of each of these parts being substantially smaller than the cross sectional area of the associated first section.

The connector member makes direct contact with the reduced parts of the second wire sections. Because of the manner in which the connector member is made, as will become apparent hereinafter, it is formed with a seam which extends in the direction of wire elongation. A continuous face of the connector member opposite the seam and directed away from the same is formed with a recess whose bottom face slopes toward the seam in the direction of wire elongation, and the portion of the bottom face nearest the seam is longitudinally coextensive with the reduced parts of the wires. The width of the recess transversely to the wires is not much smaller than the corresponding width of the connector member and substantially greater than one half of the width of the afore-mentioned continuous face.

The connector is crimped about the wires, and its recess is formed in a die having a bottom wall and two opposite side walls, the walls defining a die cavity having an open side spacedly opposite the bottom wall between the side walls. The bottom wall has an elongated ridge spacedly intermediate the side walls and two face portions of concavely arcuate cross section about respective axes extending longitudinally of the ridge and 7 connecting the ridge to the side walls. A ram drives a blank having an approximate U-shape into the cavity and crimps the blank by sliding contact with the die walls.

A front face of the ram opposite the bottom wall of the die has a rounded crest and flares from the crest in a direction away from the bottom wall. The crest of the front face is transverse to the ridge of the bottom wall in the die, and the front face is preferably cylindrically convex about an axis transverse to the axes of curvature of the two portions of the bottom wall in the die.

During operation of the apparatus, respective transversely juxtaposed portions of two metallic wires carrying respective coatings of insulating material less ductilethan the metal of the wires are enclosed the metallic'connector member which is then clampedabout the wire portions in a substantially closed loop about the longitudinal wire axes. The connector member with the wires clamped therein is confined in all directions perpendicular to the wire axes to prevent enlargement in these directions, and the confined connector member and the wire portions clamped therein are compressed in one of the perpendicular directions until the length of the connector member and of the wire portions in the direction of the wire axes is increased sufficiently to cause disruption of the insulating coatings, and direct 'metal-to-metal contact between the wire portions and the connecting member is established.

The mechanical strength, more specifically the tensile strength of the splice is at least equal to that of the original wires, if the compression is greatest in a part of the connector member which is axially central, and de' creases from the central part in both axial directions.

Other features and many of the attendant advantages of this invention will readily become apparent from the following detailed description of preferred embodiments, when considered in connection with the appended drawing in which:

FIG. 1 is a front elevational view of apparatus of the invention;

FIG. 2 shows the shaping tools and associated elements of the apparatus of FIG. 1 in an exploded, perspective view generally taken from; the rear of the apparatus;

FIG. 3 shows a detail of the device of FIG. 2 in side elevation;

FIG. 4 shows some of the shaping tools of FIG. 2 and a metal strip or flat wire engaged by the tools, the view being in partly sectional front elevation and on a larger scale than FIG. 2;

FIG. 5 is a fragmentary and further enlarged view of the strip of FIG. 4 after an initial stage of the shaping operation;

FIG. 6 shows a connector made from the strip by the tools of FIG. 2 in a perspective view approximately on the scale of FIG. 5;

FIG. 7 shows a group of the shaping tools of FIG. 2 ready to crimp the connector of FIG. 6 about two wires to be connected, the view being in front elevation, partly in section, and on a larger scale than FIG. 4;

FIG. 8 partly illustrates the device of FIG. 7 after the crimping step;

FIG. 9 further illustrates the device of FIG. 8 after completion of the splice;

FIG. 10 illustrates the splice removed from the apparatus of FIG. 1 in fragmentary side elevation; and

FIG. 11 shows the strip used for making the connector in greatly enlarged cross section.

Referring now to the drawing in detail, and initially to FIG. 1, there is seen a cast iron stand 1 which supports the operating elements of the illustrated apparatus and whose horizontal bottom face normally rests on a work bench or table, not itself shown. An electric motor 2 mounted atop the stand or frame 1 is controlled by a toggle switch 3 on a control box 4 mounted on the stand 1. A belt 6 connects the motor 2 with the input pulley of a single revolution clutch 5, not otherwise shown in detail, since it is a staple article of commerce (The Hilliard Corp., Elmyra, N.Y.). A pedal switch 7 is connected to the non-illustrated triggering solenoid of the clutch through the control box 4 in a conventional manner to connect the output shaft 8 of the clutch to the pulley 5 for one revolution when the switch 7 is closed.

A reel 9 rotatable on the frame 1 carries a coiled strip or flat wire 10 whose free end is trained over an arcuate guide plate 11 and between two identical feed cams 12 into a metal tube 13 leading to the shaping and attaching station of the apparatus. A fixed die plate 14 is the only tool of the apparatus fully visible in FIG. 1. It is releasably mounted on acarrier 15 which may be adjusted on the frame 1 by means of a spindle 16 and associated nuts. The die plate 14 is exposed in all directions, and access to the die cavity may be had at right angles to the plane of FIG. 1 by wires to be connected, there being ample space to accomodate even voluminous circuit elements which may be attached to the wires.

Each feed cam 12 is mounted on a shaft 17 and has a circularly arcuate cam face 18 centered in the axis of the shaft 17 and having a length of about 90. A slot 19 extending from one end of the cam face 18 approximately along the chord of the face into the body of each cam 12 gives some resiliency to the circularly arcuate cam portion whose radius is approximately equal to one half of the spacing of the axes of the shafts 17.

The shafts 17 are connected with each other and with the clutch output shaft 8 by a gear train of which only a spur gear 20 on the shaft 8 is indicated in FIG. 1, and which turns the shafts 17 for one revolution in opposite directions when the switch 7 is closed. Set screws, not themselves visible in the drawing, permit the cams 12 to be angularly adjusted on the shafts 17. The cams feed the strip 10 into the tube 13 as long as the cam faces 18 cooperate to grip the strip. The length of the cooperating portions, and the corresponding length of the strip 10 which is fed into the tube 12 during each revolution of the shaft 8 may thus be adjusted by setting the cams on the shafts 17.

FIG. 2 shows the shaping tools which convert the wire or strip 10 into a sequence of connectors, and attach each connector to wires inserted into the cavity of the die 14. An axial crank pin 21 projects eccentrically from the gear 20 illustrated in FIG. 2 in phantom view, and better seen in FIG. 3. Two heavy links 22, 23 are freely pivoted on the pin 21 and on respective pins 24, 25 on end portions of two elongated superposed slides 26, 27. The slides are guided longitudinally in a groove of the machine stand I normally closed by a cover 34 (FIG. 1). When the gear 20 makes one revolution, the slides reciprocate longitudinally once.

The longer slide 26 carries two spacedly juxtaposed elongated bars 28, 29 on its end remote from the pin 24 which projects beyond the slide 27 in all operative positions of the apparatus. A narrow elongated ram 30 longitudinally projects from the slide 27 into the conforming guide channel between the bars 28, 29 which function as bending tools, as will presently become apparent. The exposed terminal face 31 of the ram 30 is cylindrically arcuate and convex. The ram 30 moves into and out of the cavity in the die plate 14 during its longitudinal reciprocating movement.

The die plate 14 is approximately U-shaped about its cavity which has a concavely arcuate bottom wall opposite the ram face 31, as will be described in more detail hereinafter. The die plate is releasably, but fixedly fastened in a slot 32 of the carrier 15 by screws 33 in all operative conditions of the apparatus.

An anvil 35 is mounted on the stand 1 by means of a pivot pin 36 and biased by a strong helical compression spring 37 toward an operative position in which a flat transverse abutment face 38 on a relatively narrow blade portion of the anvil, largely obscured in FIG. 2, is directed away from the die plate 14 and opposite the terminal face 31 in the path of the ram. The blade portion of the anvil 35 also has an obliquely inclined cam face 39 contiguous to the abutment face 38. It is dimensioned to fit the guide channel between the bending tools 28, 29 with respective clearances not significantly greater than the thickness of the strip 10. Movement of the anvil 35 beyond the operative position under the urging of the spring 37 is prevented by engagement of respective vertical faces of the anvil and of the tools 28, 29.

The strip 10 is fed to the shaping tools through a slot 40 in a guide block 41 normally mounted on the frame 1 in a fixed, but adjustable position by means of a screw (not shown) passing through an elongated aperture 42 of the block 41. An edge face of the block 41 which intersects the end of the slot 40 has alternating ribs and grooves 43 which engage mating grooves and ribs on the bending tool 28 in the assembled condition of the apparatus for precisely guiding longitudinal movement of the slide 26 and of the tools 28, 29. The slot 40 is downwardly bounded by an insert 44 in the block 41 which will presently be described in more detail.

A stop 45 is spaced from the bending tools 28, 29 in a direction away from the guide block 41 and is adjustable in the direction of strip movement on a forked bracket 45 fixedly mounted on the stand 1 in a nonillustrated manner. The stop 45 may be secured in its adjusted position by means of a screw 47 passing through the two branches of the bracket 46 and a slot 48 in the stop. 46

The operation of the afore-described apparatus, and additional structural details will now be described with reference to FIGS. 4 to 8.

The distance over which the strip 10 is fed by the cams 12 is not determined by the angular setting of the cams with sufficient precision for making connections of extremely small dimensions. The strip 10 itself and the tube 13 are slightly resilient so that the effective distance between the earns 12 and the opperating station of the machine cannot be known precisely. The strip 10, as is shown in FIG. 4, is therefore fed through the slot or channel 40 in the guide block 41 against the fixed stop or abutment 45. The cams 12 are set to provide a slight excess of strip length. The strip 10 buckles slightly after hitting the stop 45 and resumes its initialshape after it is released by the earns 12.

The abutment face 38 of the anvil 35 is normally aligned in a common plane with the exposed face of the insert 44 in the slot 40, and the bending tool 28 is moved into engagement with the lending strip portion immediately after the latter strikes the stop 45 so that buckling is limited to that portion of the strip which is outside the operating station proper.

The bending tool 28 has a projecting shearing edge 54 bounded by a longitudinal face of the tool perpendicular to the plane of FIG. 4 and by the bottom face or bending face of the tool which is otherwise flat and recessed relative to the edge 54. The front end 55 of the insert 44 is rounded or beveled. Ribs and grooves aligned with the ribs and grooves 43 extend through the shearing edge 54 and the rounded front end 55 of the insert as is shown in FIG. 2, but not visible in FIG. 4.

When the slide 26 moves toward the die plate 14 in the direction of the arrow in FIG. 4, the shearing edge 54 first deflects the strip 10, which is unsupported between the anvil 35 and the insert 44, bending it over the front end 55 of the insert 44, and ultimately severs a blank 56 from the remainder of the strip 10, as partly shown in FIG. 5. The leading transverse edge of the strip and the trailing edge of the blank 56 arebent arcuately out of the plane defined by theabutment face 3 8. The second and each subsequent blank 56 have partly rolled or arcuately bent leading and trailing transverse edges 60. Because of the configuration of the shearing tools 54, 56, the transverse edges 60 of the 1 blank are toothed or scalloped.

Immediately after blanking, the bottom faces of the bending tools 28, 29 abuttingly engage the blank 56 and drape it over the anvil 35. The spring 37 is strong enough to prevent movement of the anvil under the stresses transmitted by the relatively soft material of the blank 56. However, work hardening of the strip material as it is being bent along the edges of the anvil face 38 causes the central portion of the blank to assume a convexly arcuate shape about an axis of curvature perpendicular to the plane of FIG. 4. The connector 57 formed by the bending step is seen in FIG. 5. It is moved outward of the guide channel between the bending tools 28, 29 by the now descending 'ram 30, and the anvil is thereby pivoted out of its operative position and out of the path of the ram as the connector 57 slides over the cam face 39 of the anvil.

The bending faces of the tools 28, 29 ultimately abut against the die plate 14 and the connector 57 is shifted by the ram 30 into the die cavity as is seen in FIG. 7. The arcuate terminal front face 31 of the ram 30 is cylindrical about an axis of curvature which is parallel to the plane of FIG. 7. Initial contact of the face 31 with the connector 57 is limited to the rounded, downwardly directed crest 58 of the ram face 31.

The cavity of the die plate 14 which is of uniform cross section in all planes parallel to that of FIG. 7 has side walls which flare slightly toward the open top side jointly covered by the tools 28, 29 and the ram 30 in the position of the apparatus shown in FIG. 7. The bottom wall of the cavity has two concavely arcuate face portions which meet in an elongated angular ridge 59, and whose axes of curvature are perpendicular to that of the ram face 31 and parallel to the ridge 59.

As the connector 57 is driven by the ram 30 toward the bottom wall of the die cavity, its edges 60 follow the contour of the side walls and of the arcuate bottom wall portions and the connector is crimped in a substantially closed loop about respective terminal sections of two varnish-coated magnet wires 61, 62 of uniform, circular cross section which were previously introduced into the die cavity and respectively project from the same in a foreward and rearward direction. The crimped connector and the wires enclosed and firmly clamped therein, but not significantly distorted at this stage are seen in FIG. 8. The varnish coating is too thin to be capable of pictorial representation in the drawing.

The ram 30 moves further inward of the die cavity of the terminal position seen in FIG. 9 in which substantially the entire front face 31 thereof conformingly engages the crimped connector 57 which is confined in all directions perpendicular to the wire axes to prevent enlargement thereof. The connector together with the confined wire sections clamped therein is extruded from the die cavity longitudinally of the wires and of the ridge 59 both forward and rearward. The ductile copper core of each wire is flattened in the portion of the die near the crest 58 and the longitudinal center of the ridge 59, but the relatively brittle varnish coating is disrupted into flake-shaped particlles whose combined areais much smaller than that of the copper surface exposed by the longitudinal stretching of the wire ends and in direct contact with the inner surface of the connector 57. The length increase in the connector member can readily be made percent without significantly reducing the tensile strength of the splice, but many insulating varnishes can .be disrupted by a length increase of 25 percent, and most by an increase of 35 percent.

In the presently preferred die plate 14, the ram 30 also causes a narrow rib 63 of connector metal to be extruded between each of two longitudinal walls of the ram 30 which are parallel and flat and the flaring side walls of the die cavity, and such ribs are desirable where high rigidity of the splice ultimately formed is required. The ribs can be minimized or eliminated by re ducing the angle between the side walls of the die plate 14 and by tapering the ram 30 so that the gaps between the ram 30 and the die plate 14 during the terminal phase of the ram stroke are too narrow to receive metal from the connector 57.

As is evident from FIGS. 8 and 9, upward withdrawal of the bending tools 28, 29 starts while the ram 30 still moves inward of the die plate 14, and ultimately the ram is withdrawn, permitting the finished splice shown in FIG. 10 to be removed from the apparatus, and another pair of magnet wires to be introduced for forming the next splice.

The configuration of the splice is evident from joint consideration of FIGS. 9 and 10. The sections of the wires 61, 62 which project from the connector 57 are of circular and uniform cross section and carry the original insulating varnish coating. The terminal wire sections about which the connector 57 is crimped are transversely juxtaposed between side faces of the connector and the seam formed on the underside of the connector by the edge portions 60 The terminal wire sections taper inward of the connector from the shape and cross sectional area of the undistorted section to the shape seen in FIG. 9. The parts of the wires 61, 62 located between the crest 58 of the ram face 31 and the bottom wall of the die in FIG. 9 are flattened substantially in a common plane,

and of sharply reduced cross sectional area. Their insulating varnish coating, not itself visible in the drawing, is broken up into particles sufficiently spaced from each other so as not to interfere significantly with cur.- rent flow between the wires through the connector.

The external top face connector the connecotr 57 opposite the seam of the edges 60 and directed away from the same is formed with a recess whose bottom face 64 approximately duplicates the curvature of the ram face 31. It slopes toward the bottom seam in the connector, and the portion of the bottom face 64 which is nearest the seam is coextensive with the reduced, flattened parts of the wires 61, 62 in the direction of wire elongation. The bottom wall 64 extends between the two lateral ribs 63, but its width is almost equal to the uniform width of the connector 57, and much greater than one half of the connector width. Because of the presence of the ribs 63, the splice is not readily bent across its thinnest portion where the bottom face 64 approaches the seam, but may be bent by a force sufficient for stretching the ribs which tend to fold down on the bent bottom face 64.

Insulated magnet wires of the smallest commercial diameters, but also of larger diameters have been spliced successfully under continuous production conditions on apparatus on which the splices were formed between the same die having an elongated ridge in its bottom face and the same ram whose front face was arcuate about an axis of curvature transverse to the elongation of the ridge. When tensioned, the spliced wires broke at random locations indicating that the wires were not weakened by the splice.

Under difficult conditions, splices of highest conductivity are produced from approximately flat wire or strip of the type shown in FIG. 11 and produced by broaching an initially flat major face of a strip of approximately reactangular cross section. The grooves 65 formed by the broaching tool leave ribs 66 spacedly juxtaposed and running lengthwise on the strip. Burrs 67 project from the longitudinal top edges of the ribs 66.

In the finished splice, the ribs 66 extend from the bottom seam around the terminal wire portions and back to the seam from the opposite side. The burrs cut into the insulating layer during the crimping stage, and the breaks formed thereby in the lacquer coating facilitate the disintegration of the insulating film during the subsequent extrusion of the wires from the die plate 14. In magnet wires having a relatively heavy insulating coating, the force required for deforming the slice from the condition of FIG. 8 to that of FIG. 9 is significantly reduced by the use of ribbed and sharp-edged strip material of the kind shown in FIG. 11.

It should be understood, of course, that the foregoing description relates only to preferred embodiments of the invention, and that it is intended to cover all changes and modifications in the examples of the invention herein chosen for the purpose of the disclosure which do not constitute departures from the spirit and scope of the invention set forth in the appended claims.

What is claimed is:

1. [man apparatus for splicing wires including shaping means for shaping a blank of strip material into an approximate U-shape, die means including a bottom wall and two opposite side walls, said walls defining a die cavity having an open side spacedly opposite said bottom wall between said side walls, said bottom wall having an elongated ridge spacedly intermediate said side walls and two face portions of concavely arcuate cross section about respective axes extending longitudinally of said ridge and connecting said ridge to said side walls respectively, a ram member, moving means for moving said ram member inward of said cavity through said open side toward said bottom wall, and means for placing the shaped blank in the path of movement of said ram member for insertion of the blank into said cavity by said ram member and crimping of the blank by sliding contact with said walls, the cavity being open longitudinally of said ridge for insertion of wires to be spliced, the improvement which comprises:

a. said ram member having a front face opposite said bottom wall,

b. said front face having a crest and flaring from said crest in a direction away from said bottom wall,

c. the crest of said front face being transverse to the ridge of said bottom wall.

2. In an apparatus as set forth in claim I, said front face being of convexly arcuate cross section about an axis transverse to the axes of curvature of said two face portions of said bottom wall in said die.

3. In an apparatus as set forth in claim 2, said cavity being of uniform cross section transverse to said ridge in the bottom wall substantially over the length of said ridge.

4. In an apparatus as set forth in claim 3, said front face being of uniform cross section transversely to said axis thereof over an axial length substantially greater than one half of the width of said bottom wall between said side walls.

5. In an apparatus as set forth in claim 3, said front face having an axial length substantially greater than one half of the width of said bottom wall between said side walls. 

1. In an apparatus for splicing wires including shaping means for shaping a blank of strip material into an approximate Ushape, die means including a bottom wall and two opposite side walls, said walls defining a die cavity having an open side spacedly opposite said bottom wall between said side walls, said bottom wall having an elongated ridge spacedly intermediate said side walls and two face portions of concavely arcuate cross section about respective axes extending longitudinally of said ridge and connecting said ridge to said side walls respectively, a ram member, moving means for moving said ram member inward of said cavity through said open side toward said bottom wall, and means for placing the shaped blank in the path of movement of said ram member for insertion of the blank into said cavity by said ram member and crimping of the blank by sliding contact with said walls, the cavity being open longitudinally of said ridge for insertion of wires to be spliced, the improvement which comprises: a. said ram member having a front face opposite said bottom wall, b. said front face having a crest and flaring from said crest in a direction away from said bottom wall, c. the crest of said front face being transverse to the ridge of said bottom wall.
 2. In an apparatus as set forth in claim 1, said front face being of convexly arcuate cross section about an axis transverse to the axes of curvature of said two face portions of said bottom wall in said die.
 3. In an apparatus as set forth in claim 2, said cavity being of uniform cross section transverse to said ridge in the bottom wall substantially over the length of said ridge.
 4. In an apparatus as set forth in claim 3, said front face being of uniform cross section transversely to said axis thereof over an axial length substantially greater than one half of the width of said bottom wall between said side walls.
 5. In an apparatus as set forth in claim 3, said front face having an axial length substantially greater than one half of the width of said bottom wall between said side walls. 